U.S. Pat. No. 6,335,035 ('035) to Drizen, et al. is a divisional of U.S. Pat. No. 6,063,405 to Drizen et al. which teaches sustained release compositions comprising a drug dispersed within a polymer matrix, methods of producing the same and treatments with the complex. The '035 patent discloses a sustained drug delivery system, which comprises a drug dispersed within a polymer matrix solubilized or suspended in a polymer matrix. The polymer matrix is composed of a highly negatively charged polymer material selected from the group consisting of polysulfated glucosoglycans, glycoaminoglycans, mucopolysaccharides and mixtures thereof, and a nonionic polymer selected from the group consisting of carboxymethylcellulose sodium, hydroxypropylcellulose and mixtures thereof. Nonionic polymers are generally used in amounts of 0.1% to 1.0% and preferably from 0.5% to 1.0%. Nonionic polymers in amounts above 1.0% are not used as they result in the formation of a solid gel product when employed in combination with an anionic polymer.
U.S. Pat. No. 6,692,766 to Rubinstein et al. concerns a controlled release drug delivery system comprising a drug which is susceptible to enzymatic degradation by enzymes present in the intestinal tract; and a polymeric matrix which undergoes erosion in the gastrointestinal tract comprising a hydrogel-forming polymer selected from the group consisting of (a) polymers which are themselves capable of enhancing absorption of said drug across the intestinal mucosal tissues and of inhibiting degradation of said drug by intestinal enzymes; and (b) polymers which are not themselves capable of enhancing absorption of said drug across the intestinal mucosal tissues and of inhibiting degradation of said drug by intestinal enzymes.
U.S. Pat. No. 6,716,251 to Asius et al. discloses an injection implant for filling up wrinkles, thin lines, skin cracks and scars for reparative or plastic surgery, aesthetic dermatology and for filling up gums in dental treatment. The invention concerns the use of biologically absorbable polymer microspheres or microparticles suspended in a gel.
U.S. Pat. No. 6,586,493 to Massia et al. discloses hyaluronate-containing hydrogels having angiogenic and vascularizing activity and pre-gel blends for preparing the hydrogels. The hydrogels contain a cross-linked matrix of a non-angiogenic hyaluronate and a derivatived polysaccharide material, in which cross-linking is effected by free-radical polymerization.
The literature also teaches the properties of polymer matrices and their use as drug delivery vehicles (Xu et al. Langmuir, (2004) 20(3): 646-652., Liang et al. Biomacromolecules, 2004. 5(5):1917-25, Ohya et al. Biomacromolecules (2001) 2:856-863 Cho et al. International Journal of Pharmaceutics (2003) 260:83-91, Kim et al. Journal of Controlled Release (2002) 80:69-77, Tate et al. Biomaterials (2001) 22: 1113-1123, and Silver et al., Journal of Applied Biomaterials (1994) 5: 89-98).